Tape storage device for storing audio data in the amble frames of a DDS format tape

ABSTRACT

A helical-scan tape storage device is operative to write computer data to tape according to a predetermined format in which the data is store in tracks arranged in groups. These groups are optionally separated by one or more amble track To enable auxiliary data, such as audio data to be stored within the format, the storage device is arranged to store a succession of N ambles into which the auxiliary data is written. Using the amble tracks to store auxiliary data permits storage devices that have been designed only with regard to computer data storage to read tapes containing both computer and auxiliary data, since the auxiliary-data-containing amble tracks are ignored by such a device. A storage device designed to extract auxiliary data from ambles can readily recover the auxiliary data.

FIELD OF THE INVENTION

The present invention relates to a tape storage device and inparticular, but not exclusively, to a tape storage device intended forstoring host computer data but which can also be used to store audiodata.

BACKGROUND OF THE INVENTION

Tape storage devices for writing data to tape are known of the typecomprising helical-scan recording means operative to write to tape in asuccession of tracks each having a data area for the storage of data;and signal processing means operative to receive first data signals,representative of first data to be stored, and to process said firstdata signals to generate and output track signals to said recordingmeans whereby to cause the latter to write the first data to tape inaccordance with a predetermined format in which said first data isstored in the data areas of one or more groups of tracks with furthertracks, hereinafter "amble" tracks, being used to perform auxiliaryfunctions, the said groups of tracks and said amble tracks being such asto permit them to be distinguished from each other upon reading. Suchtape storage devices are generally also arranged to read tapes writtenin accordance with said predetermined format, although a separate tapestorage device may be provided for this purpose. Thus, tape storagedevices for reading data from tape are known of the type comprisinghelical-scan reading means operative to read a tape written inaccordance with said format and to output track signals representativeof the tracks recorded thereon; and signal processing means operative toreceive said track signals from the reading means and to process saidtrack signals to generate and output first data signals representativeof said first data recorded in the data areas of the groups of tracks,this processing involving distinguishing signals derived from saidgroups of tracks from signals derived from said amble tracks whereby toavoid any contents of the amble tracks being treated as first data.

Tape storage devices of the aforesaid types include storage devicesoperative to write/read data to/from tape in accordance with the DigitalData Storage (DDS) format described in the document "Digital DataStorage Format Description" (Revision B, October 1988) available fromHewlett-Packard Limited, Bristol, England. The DDS format is based onthe DAT digital audio recording format but includes modifications andextensions to the basic DAT format to render it suitable for storingcomputer data. For a storage device implementing the DDS format, theaforesaid first data is constituted by the computer data, this databeing stored in groups of tracks that are optionally separated by ambletracks.

Because computer data is essentially asynchronous (by which is heremeant that it does not need to be provided at a constant transfer rate),the DDS format does not need to include the same amount of first data inevery track but can afford to have an uneven distribution of databetween tracks. More particularly, as well as the amble tracks not beingavailable for first data, at least a portion of one or more tracks ofeach said group of tracks is used to store an index of record and fileseparators relating to the first data held in the group.

For certain applications it would be useful if both computer data andaudio data could be at least read by the same DDS storage device.

One possible way of achieving this would be to arrange for the DDSdevice to be able to play a tape written on a DAT audio player. Theunderlying format of the DDS drive is the 48 KHz mode of the DATspecification so that much of the DDS storage device electronics issimilar to that of a DAT player. However, for this approach to work theDDS storage device would need to be altered to recognize the DAT formatand read the audio data, as well as cope with the absence of a lead-inarea as is provided on a DDS tape. Furthermore, that part of the DDSdevice electronics expecting to find data organized into groups wouldneed to be disabled or bypassed. Clearly, this approach would requiresubstantial redesign of a standard DDS-only tape storage device.

A different approach would be to store audio data as first data withingroups of tracks in accordance with the DDS format. However, as alreadymentioned, the storage of data in groups is really only suitable forasynchronous data rather than synchronous data, such as audio data,where a steady transfer rate is needed. In order to overcome thetransfer rate fluctuations that would be caused by amble tracks andgroup indexes a substantial data buffer would be required with theattendant cost and complexity. In addition, some way would need to befound to distinguish audio data from computer data so that the former isnot mistaken for the latter.

SUMMARY OF THE INVENTION

An object of the present invention is to provide for the writing/readingof second data, such as audio data, by tape storage devices of the abovetype.

According to one aspect of the present invention there is provided atape storage device of the aforesaid type for writing data to tape,wherein the said signal processing means is provided with insertionmeans arranged to receive second data signals, representative of seconddata to be stored, and operative to cause said second data to be writtenin the data areas of amble tracks.

Where the second data is asynchronous and small in quantity, there maybe circumstances in which the generation of amble tracks during normaloperation of the storage device to write first data, will be sufficientto meet the requirement to store the second data. However, for mostapplications it will be necessary for the signal processing means togenerate extra amble tracks for storing the second data; in particular,for high-quality audio data and similar synchronous data, the signalprocessing means will need to generate a continuous series of ambletracks for storing this data. Preferably, this is done automatically bythe signal processing means whenever second data is to be stored.

Since a tape storage device of the aforesaid type for reading data fromtape is operative to distinguish amble tracks from groups of tracksstoring the first data, there is no risk of the second data beingmistaken for the first data upon reading; however, extra circuitry willbe required to extract the second data. More particularly, according toa second aspect of the present invention, there is provided a tapestorage device of the aforesaid type for reading data from tape, whereinthe said signal processing means includes extraction means operative toextract from the data areas of said amble tracks, any second datawritten therein and to generate and output second data signalsrepresentative of any such second data.

Although the provision of second-data extraction means is clearly ofsubstantial benefit, an advantage of the present invention is in factthat data-reading devices which have not been adapted to read seconddata, will generally still be able to read first data off a tape writtenwith both first and second data.

In a known form of data-writing storage device of the aforesaid type,the signal processing means comprises a first write-processing sectionarranged to receive said first data signals and to generate intermediatesignals including signals for constituting the data areas both of saidgroups of tracks and of said amble tracks, and a second write-processingsection operative to produce said track signals from said intermediatesignals. For such devices, the insertion means for inserting second dataadvantageously comprises:

amble detection means connected to monitor said intermediate signalswhereby to detect said signals for constituting said amble data areas,and

multiplexor means connected to receive both said intermediate signalsand said second data signals and selectively operable to pass one orother of these signals to said second write processing means.

The amble detector means is connected to control said multiplexor meanssuch that the intermediate signals are normally passed to said secondwrite processing means, the second data signals only being passed to thesecond write-processing means during the time, or a portion thereof,when the amble-data-area signals are detected Where the firstwrite-processing section generates, as part of said intermediatesignals, identification signals for distinguishing between said groupsof tracks and said amble tracks, said insertion means is preferablyoperative to allow said identification signals, including thoseassociated with amble tracks, to pass unaltered to said second writeprocessing means.

As an alternative to substituting second data for the amble-body data ofpreviously-created ambles, it is of course possible to arrange forsecond data to be incorporated into ambles at their point of generation.

In a known form of data-reading storage device, the said signalprocessing means comprises a first read-processing section arranged toreceive said track signals and to generate intermediate signalsrepresentative of the contents of the data areas both of said groups oftracks and of said amble tracks, and a second read-processing sectionoperative to produce said first data signals from said intermediatesignals. For such devices, the said extraction means preferably include:

amble detection means connected to monitor said intermediate signalswhereby to detect those signals representative of the contents of saidamble data areas, and

output means connected to receive said intermediate and controlled bysaid amble detection means signals and controlled by said ambledetection means to utilize said signals representative of the contentsof said amble data areas as the second data signals.

Generally with regard to how first-data tracks are distinguished fromamble tracks, this is preferably done by generating a header for eachpair of tracks (such a pair being known as a `frame`) and storing theheader in the data areas of the corresponding frame; by including aframe identifier in the header, it is possible readily to distinguishamble frames from other frames.

The second data may be derived from a single source or from a selectedone of several sources. In this latter case, a source identifier ispreferably stored as part of the second data or as first data in anassociated group; on reading, this source identifier is examined andused to output the second data to an appropriate output channel.

BRIEF DESCRIPTION OF THE DRAWINGS

A tape storage device embodying the present invention will now beparticularly described, by way of non-limiting example, with referenceto the accompanying diagrammatic drawings, in which:

FIG. 1 illustrates the format of a frame written to tape in accordancewith the DAT format specification;

FIG. 2A shows the layout of a tape written according to the DDS format;

FIG. 2B shows the composition of a recorded data group written in a dataarea of the tape layout of FIG. 2A;

FIG. 3 is a block diagram of a tape storage device arranged to implementthe DDS format;

FIG. 4 illustrates a basic group produced by a group processor of theFIG. 3 storage device;

FIG. 5 illustrates G1 sub-groups produced by the group processor of theFIG. 3 storage device;

FIG. 6 illustrates G2 sub-groups produced by the group processor of theFIG. 3 storage device;

FIG. 7 illustrates the composition of a G3 sub-group transferred betweenthe group processor and DAT electronics of the FIG. 3 storage device;

FIG. 8 illustrates one array of twin arrays that form a G4 sub-groupproduced by the DAT electronics of the FIG. 3 storage device;

FIG. 9 illustrates the composition of a main data block produced by theDAT electronics of the FIG. 3 storage device;

FIG. 10 illustrates the composition of a sub data block produced by theDAT electronics of the FIG. 3 storage device;

FIG. 11 shows the format of track signals transferred between the DATelectronics and a DAT deck of the FIG. 3 storage device;

FIG. 12 illustrates the insertion of N ambles between two recorded datagroups;

FIG. 13 is a block diagram of audio insertion/extraction circuitry foruse with the FIG. 3 storage device;

FIG. 14 are time lines illustrating various waveforms relevant to theoperation of the FIG. 13 audio insertion/extraction circuitry.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The present invention is described below in relation to a tape storagedevice that stores and retrieves host computer data on tape generally inaccordance with the DDS (Digital Data Storage) Format jointly developedby Hewlett-Packard Limited and Sony Corporation. A detailed descriptionof the DDS format is given in the document "Digital Data Storage FormatDescription" (Revision B dated October 1988 available fromHewlett-Packard Limited, Bristol, England). The DDS format for thestorage of computer data utilizes and builds upon the 48 KHz mode of theDAT (Digital Audio Tape) format used for the storage of PCM audio data;a detailed description of the DAT format can be found in the document"DAT Conference Standard" (March 1988, Electronic Industries Associationof Japan Tokyo, Japan) The DAT format and, accordingly, the DDS format,both employ a helical-scan recording technique in which tape storagemedium is moved obliquely over a rotating head drum with a 90° wrapangle; the drum carries two read/write heads which write pairs ofoverlapping, opposite azimuth, tracks known as frames.

Tape storage devices implementing the DDS format are available, interalia, from Hewlett-Packard Limited and are generally referred to as DDSdrives.

To facilitate an understanding of the present invention, a briefoverview of the main features of the DDS format will now be givenfollowed by a description of the main functional elements of a DDSdrive.

DDS Format Overview

The basic unit for writing and reading information to/from a tape 10 isa frame FIG. 1 illustrates the format of a frame which, as alreadymentioned, is made up of two opposite azimuth tracks 20, 21. In FIG. 1,the arrow T indicates the direction of tape movement. Each trackcomprises two marginal areas 22, two sub areas 23, two ATF (AutomaticTrack Following) areas 24 and a main area 25. The ATF areas 24 providesignals enabling the heads of the head drum (not shown) to accuratelyfollow the tracks in known manner. The main area 25 is used to store thedata (host data) provided to the tape device by the host computer (thehost data comprises user data supplied as records by the host computerand separator marks that indicate logical separation of the user data).The sub areas 23 are primarily used to store auxiliary information knownas sub codes that relate for example, to certain recording parameters(such as format identity, tape parameters etc.), and tape usage history.

The general organization of frames along a tape (that is, the tapelayout) is illustrated in FIG. 2A. As can be seen, the tape is organizedinto three main areas, namely a lead-in area 36, a data area 37 and anend-of-date (EOD) area 38 The ends of the tape are referenced BOM(beginning of media) and EOM (end of media) Host data is recorded in themain areas of the frames written in the data area 37. The lead-in area36 includes a system log area, between a beginning-or-recording (BOR)mark and the data area 37, where system information is stored. A tapeArea ID sub code stored in the sub area 23 of each frame, enables thesystem log area, data area 37 and EOD area 38 to be distinguished fromone another.

As shown in FIG. 2B, the frames 48 of the data area are arranged inrecorded data groups 39 each of twenty two valid frames (plus anoptional frame 43--the C3 ECC frame--storing error correction code forthe group).

Within a group, user data and separator marks are separately stored, theuser data being stored as a continuous run of bytes across the mainareas of successive frames without record markers, while information onthe division of user data into records and the separator marks are heldin an index 40 that extends forwards from the end of the main area ofthe last frame in the group. (Note that the index will in fact bephysically dispersed within the last frame due to a byte-interleavingprocess employed during recording after formation of the index.)

These recorded data groups are separated from each other by one or moreamble frames 44 the main areas of which are filled with a randomizedall-zeroes pattern. Ambles are only permitted in the data area 37.

Further details of the DDS format will become apparent from thefollowing description of a DDS drive that implements the format.

DDS Drive

FIG. 3 is a functional block diagram of a DDS drive The devicecomprises:

an interface unit 50 for interfacing the drive with a host computer (notshown) via a bus 51;

a group processor 52 for processing user data records and separatormarks into and out of indexed groups;

DAT electronics 53 which effects low-level signal processing,substantially as specified in the DAT standard, but with certainmodifications as specified in the DDS format; this low-level processingserves to convert a byte stream supplied to it by the group processor 52into track signals ready for recording and to reconvert track signalsback into a byte stream for the group processor;

a helical-scan tape deck 54 for writing to and reading from a tapemedium; and

a system controller 55 for controlling the operation of the otherelements of the drive in response to commands received from the host viathe interface unit 50.

The drive is arranged to respond to commands from the host computer toload/unload a tape, to store a data record or separator mark, to searchfor selected separator marks or records, and to read back the nextrecord.

The interface unit 50 is arranged to receive the commands from thecomputer and to manage the transfer of data records and separator marksbetween the tape storage device and computer Upon receiving a commandfrom the computer, the unit 50 passes it on to the system controller 55which, in due course, will send a response back to the computer via theunit 50 indicating compliance or otherwise with the original commandOnce the drive has been set up by the system controller 55 in responseto a command from the computer to store or read data, the interface unit50 will also control the passage of records and separator marks betweenthe computer and group processor 52.

A description will now be given of the general operation of the drive interms of the writing of data to tape; the operation of the drive duringreading of data will be apparent to persons skilled in the art asprocesses are either simply reversed or data assembled during writing toaid the reading process is appropriately put to work during the latter(for example, error-correction codes calculated during writing are usedduring reading to correct errors).

During data storage a grouping unit 56 of the group processor 52 isarranged to organize the data that is provided to it in the form of userdata records and separator marks, into data packages referred to as"basic groups". The grouping unit 56 is also arranged to construct theindex for each basic group. The unit 56 assembles each basic group in agroup store 57 The form of a basic group is illustrated in FIG. 4 and,as can be seen, each basic group comprises 126632 bytes in all dividedbetween user data (without any record marks) and an index 40 grown fromthe end of the basic group. The index 40 itself comprises two main datastructures, namely a group information table 41 storing generalinformation about the basic group (number of records, separator marks,etc), and a block access table 42 containing more specific data on thecontents of the group (including information regarding the division ofuser data into records and the logical location of separator marks). Thegroup information table 41 is stored in a fixed location at the end ofthe group and is the same size (32 bytes) regardless of the contents ofthe basic group. In contrast, the block access table 42 varies in sizedepending on the contents of the group and extends from the groupinformation table backwards into the remainder of the user data area ofthe frames of the group. Entries are made in the block access table fromthe group information table backwards to the boundary with user data.

During data writing when the host is ready to pass a data record, theinterface 50 asks the grouping unit 56 whether it is ready to receivethe record. The grouping unit 56 may initially send a "wait" reply but,in due course, enables the transfer of the data record from the host tothe group store 57.

Typically, a host transfers records one at a time although multiplerecord transfers may be permitted for shorter records.

The record will be transferred to a group store location thatcorresponds to the eventual positioning of the record user data withinthe basic group of which it is to form a part. Information on the sizeof the record is used by the grouping unit 56 to update the group indexThe index is constructed in a location in the group store appropriate toits position at the end of a basic group.

If a transfer from the host cannot all fit inside a basic group, it issaid to "span" the group boundary. The first part of the transfer goesinto one basic group and the rest into one or more subsequent basicgroups. If no span occurs, the group index is updated and the groupingunit 60 waits for another write command. If a span occurs, the index ofthe current basic group is updated and that group is available forwriting to tape. The next group is begun and the data from the host goesdirectly into the beginning of that new basic group. When the host sendsa separator mark the grouping unit 56 will update the index of thecurrent basic group accordingly.

The grouping unit 56 also generates certain sub-codes relevant to thecurrent basic group such as the number of separator marks and recordsreceived counted from the first group.

During data writing, each basic group is transferred out of the groupstore in twenty two blocks each of 5756 bytes known as G1 sub-groups(see FIG. 5). Each such sub-group eventually forms the data contents ofa respective recorded frame. Each G1 sub-group is allocated anidentifying number known as the logical frame identification number(LF-ID) which the grouping unit 56 incorporates into a header. Thisheader is subsequently combined into the main data stream along with theassociated G1 sub-group (see below).

Optionally, the grouping unit may also calculate an error correctioncode (C3 code) block for each basic group. This C3 code forms its own G1sub-group that is appended as a twenty third sub-group to the stream ofsub-groups transferred out of the grouping unit.

When data is being read from tape, the grouping unit 56 is arranged toreceive G1 sub-groups and write them into the group store 57 in such amanner as to build up a basic group. The grouping unit 56 can thenaccess the group index to recover information on the logicalorganization (record/entity structure, separator marks) of the user-datain the group. Using this information, the group processor 52 can pass arequested record or separator mark to the host via the interface 50. Theassembly of G1 sub-groups back into a basic group is facilitated by theassociated logical frame IDs provided to the grouping unit 56 in theheaders stripped from the sub-groups earlier in the reading process.

Returning now to the description of the data writing process, the G1sub-groups output from the grouping unit 56 are subject to a randomizingprocess, of known form, in randomizer 58 in order to provide aconsistent RF envelope on the read signal, independent of the datapattern in the frame. The output of the randomizer 58 is a succession ofG2 sub-groups (see FIG. 6).

One or more amble sub-groups may optionally be added to the end of eachgroup of G1 sub-groups fed to the randomizer 58, the control of ambleaddition being effected by an amble-control functional unit 45 of thegroup processor 52. These amble sub-groups are written to tape as ambleframes. The contents of an amble sub-group are constituted by zero byteswhich after processing (including randomizing in randomizer 58) form thecontents of the main area 25 of the corresponding amble frame, the onlydata in these main areas being a header associated with each amble. Themain purpose of adding in amble sub-groups is to permit uninterruptedwriting by the deck 54 if, for any reason, there is a delay in providingthe next following group for writing to the deck. Thus, for example, ifthere is a delay in providing host data to the processor 52 to completethe next basic group, the unit 45 oversees the insertion of one or moreamble sub-groups until such time as the processor 52 can complete thenext basic group (or until a time-out has been reached and continuouswriting is terminated, whereupon a repositioning operation must occurbefore the next group is written to tape) Any number of amble frames maybe written to tape after a recorded data group.

The header associated with each amble sub-group is generated by thegrouping unit 56 when the amble-control unit 45 determines that an amblesub-group is to be inserted The logical frame ID of the header is set tozero to indicate that the sub-group is an amble sub-group and thereforemay be ignored during reading when the sub-group is passed to the groupprocessor 52. The sub codes to be recorded in the sub-areas of an ambleframe are also provided by the grouping unit 56 and, in fact, comprisesub codes relevant to the last preceding group.

Following the randomizer 58, a multiplexer/demultiplexer 59 combineseach G2 sub-group with its header and with a number of all-zero paddingbytes needed to conform the size of each sub-group with the audio dateframe size of the DAT format. The output of the mux/demux 59 isconstituted by a succession of G3 sub-groups each of 5824 bytesconceptually arranged as illustrated in FIG. 7 (this arrangement andterminology matches the DAT format). More particularly, the bytes arearranged in rows of four as two 2-byte words, each word being labelledeither a channel A word or a channel B word (reflecting the audioassociations of the DAT format). The two words in the first row(numbered 0) are constituted by the sub-group header, the words in rows1 to 1439 are derived from the corresponding G2 sub-group, and the wordsin rows 1440 to 1455 are the all-zero padding bytes.

As noted above, the header for each sub-group is generated by thegrouping unit 56 and is provided in coordination with the output of thecorresponding G1 sub-group. The structure of the header of eachsub-group can be seen from FIG. 7. Again, as already noted, the headercontains a Logical Frame ID (LF-ID); this ID is a one byte code storedin the upper byte position of both channels A and B. The first six bitsof the LF-IF indicate the running number of each sub group within agroup (1 to 23, the optional C3 frame being frame 23) or is set to zerofor an amble frame. Bit seven of the LF-ID is set to ONE to indicate thelast sub-group of a group (inclusive of any C3 sub-group). Bit eight ofthe LF-ID is set to ONE only for a C3 sub-group. In addition to theLF-ID, the header includes a four-bit data format ID (stored in thelower byte position of both channels A and B) which for the DDS formatis set to 0000.

The G3 sub groups are passed to a main data processor 60 of the DATelectronics 53 where they are processed substantially in accordance withthe 48 KHz mode of the DAT format. More particularly, the bytes of eachG3 sub-group undergo an interleaving process to form twin arrays as theyare fed into an interleave store 61 of the main data processor 60. Thisinterleaving minimizes the effects of certain media defects. Two sets oferror correcting codes (C1 and C2) are then generated and inserted intothe twin arrays held in store 61. FIG. 8 illustrates the conceptual formof one of these twin arrays that together constitute a G4 sub group. Ascan be seen from FIG. 8, each array of a G4 sub group is formed by 128columns each of 32 bytes. After further processing in the DATelectronics 53, the two arrays of a G4 sub-group will form the contentsof the main area of respective tracks of a frame.

Each array of a G4 sub-group is next formed into 128 main data blocks(see FIG. 9) each of 35 bytes by combining the 32 bytes of each arraycolumn with a three-byte Main ID in a block multiplexer/demultiplexer62. The Main ID bytes are provided by a main ID unit 63 and areconstituted by two bytes W1, W2 and a parity byte. Byte W1 containsformat ID and frame number information and byte W2 contains a blocknumber identifying the current main data block within the set of 128blocks derived from each G4 subgroup group array.

By the foregoing process, each basic group is transformed into 22 pairsof 128 main data blocks (that is 5632 main data blocks) with a furtherpair of 128 blocks for the C3 and each amble sub-group if present.

In parallel with the generation of the main data blocks, 35-bytesub-data blocks are also generated that contain sub codes supplied tothe DAT electronics 53 from the group processor 52 and system controller55. Thirty two sub-data blocks are generated for each G4 sub groupprocessed (that is, 8 blocks for each of the two sub areas 23 of the twotracks into which the G4 sub group is to be written).

The structure of a sub-data block is illustrated in FIG. 10. Each subdata block comprises a three-byte "Sub ID" section 33 and a thirty-twobyte "Sub Data" section.

The Sub ID is generated in a sub ID unit 64 and is composed of twoinformation-containing bytes SW1, SW2 and a parity byte. Byte SW2 isused for storing information relating to the current sub data block as awhole (type and address) and the arrangement of the Sub Data sectionByte SW1 is used for storing sub codes and in particular, the Area IDindicating the current tape area (this sub code is supplied by thesystem controller 55).

The Sub Data section of each sub data block is generated in unit 65 andis composed of thirty two bytes arranged into four eight-byte "packs".Each pack is used to store a pack item; there are a number of differenttypes of pack item each holding a particular set of sub codes. Themapping of pack items into the sub data packs is dependent on thecurrent tape area and not all pack items will be present in any giventape area. The identity of the pack item held in a sub-data pack isindicated by a pack-item code that occupies the first half byte of eachpack item stored in a pack. With regard to the fourth pack, for everyeven block this pack is either set to zero or contains the same packitem as the third pack, while every odd block the fourth pack contains aC1 parity byte for the first three packs of the current block and allfour packs of the preceding even-numbered sub-data block.

By way of example, pack items coded 1 and 2 contain group, separator,and record counts while pack items 3 and 4 both contain area ID,absolute frame number, LF-ID and check sum data. Pack 3 of every odd subdata block contains pack item 3 while pack 3 of every even sub-datablock contains pack item 4.

Certain of the sub code data stored in the packs are cumulative totalsof events (such as number of groups) taken from BOR. This is madepossible by storing historical data on such events in the packs of thesystem log area at the end of each tape usage session and thenretrieving this data at the start of a new session.

The sub-ID bytes and the packs of the sub-data section are assembledinto sub-data blocks by a sub-data block multiplexor/demultiplexor 66.

The final step in the writing process is to generate the track signalscontaining the main data blocks and sub data blocks. In order to avoidundesirable flux transitions, each 8-bit byte of the main data andsub-data blocks is transformed into a suitable 10-bit pattern, theresultant bits being termed "channel bits". This transformation iscarried out by the 8-10 transformation unit 67 shown in FIG. 3.

After this transformation, a predetermined 10-channel-bit sync field isadded to the front of each transformed main data and sub data blockthereby forming 360-channel-bit blocks referred to as "recorded maindata blocks" and "recorded sub data blocks" respectively. This operationis carried out by multiplexor/demultiplexor 68.

Finally, the recorded data blocks are combined with other types of360-channel-bit recorded blocks (described below) inmultiplexor/demultiplexor 69 to form track signals to be fedalternatively to the head HA and HB of the head drum 70 of the desk 54.

The sequence of recorded blocks does, of course, determine the format ofeach track (this format has already been described in general terms withreference to FIG. 1). A more detailed break down of the composition ofeach track in terms of recorded blocks is shown in FIG. 11. As can beseen, each track contains 196 recorded blocks with the 128 recorded maindata blocks corresponding to one array of a G4 sub-group, being recordedbetween two groups of eight recorded sub data blocks. In addition tothese recorded main data blocks and recorded sub data blocks, thefollowing recorded block types are present:

Margin block, preamble blocks and postamble blocks (repeated channelbits pattern "111")

Spacer blocks (repeated channel bits pattern "100")

ATF blocks (predetermined frequency patterns).

The helical scan tape deck 54 is of standard form compliant with DATspecifications and will not be described in detail herein. The low-levelcontrol of the deck is effected by a servo unit 71 which itself iscontrolled by the system controller 55 The unit 71 also indicatesbeginning-of-media (BOM) and end-of-media (EOM) conditions to thecontroller 55. Included within the servo unit 71 is automatic trackfollowing (ATF) circuitry that, during writing, generates the ATF blocksand, during reading, utilizes the ATF signals provided by the heads HA,HB to ensure proper alignment of the heads with the tracks recorded onthe tape.

The deck 54 also has a pulse generator 72 arranged to generate a pulseoutput once every revolution of the head drum 70. This pulse outputconstitutes a frame timing signal FTS as each drum revolutioncorresponds to the reading/writing of one frame. The FTS signal isphased to mark the beginning of each frame and is used to synchronizethe operation of the DAT Electronics and the transfer of data to/fromthe grouping unit 56, with the operation of the deck 54.

It will be appreciated that the foregoing description of the FIG. 3drive has concentrated on the functional components of the drive ratherthan any particular implementation of this functionality. In practice,the processes of the group processor 52 and DAT electronics 53 can beimplemented by respective controlling microprocessors with associatedapplication-specific circuitry.

The functioning of the drive during the reading of data is substantiallya reverse of the above described write operation but with certain of theauxiliary data assembled during writing being utilized to aid thereading process (for example, error correction codes, block addresses,logical-frame ID).

Furthermore, as well as normal-speed writing and reading, the drive willgenerally be provided with a fast search capability involving readingthe sub areas of occasional frames to locate a desired record.

Audio in DDS

An adapted form of the above DDS drive, embodying the present invention,is described below. This embodiment permits audio data to be recordedwithin the DDS format without affecting the reading of host data by astandard DDS drive. This is achieved by using amble frames to storeaudio data. As already noted, the main data area of an amble framecontains no host data, only scrambled zeroes and a four-byte headerholding the logical frame ID (LF-ID). Provided the header with its LF-IDis retained, the rest of the main area of an amble frame can be used tostore audio data; because the LF-ID of the frame corresponds to an ambleframe, this data is ignored by the group processor 52.

More particularly and with reference to FIG. 7, for each G3 sub-group,words 1 to 1455 of both channels A and B are used to store audio data,while words 0 of both channels are kept as the sub-group header with itsLF-ID set to zero.

Preferably, but not necessarily, the same audio encoding is used for theaudio data inserted into amble frames as is used in the DAT standard.This facilitates recording and reproduction, though account needs to betaken of the fact that the header is not audio data.

To write any significant amount of audio data, it is, of course,necessary to use a succession of N ambles; FIG. 12 illustrates a blockof N ambles recorded between groups 39 containing host data. Uponstandard DDS drive reading a tape formatted as in FIG. 12, it willsimply ignore the amble frames and only output back to the connectedhost the contents of the groups 39. However, the embodiment of thepresent invention described below, will extract audio data contained inthe ambles and reproduce the original recorded audio.

The embodiment of the invention illustrated in FIG. 13 is intended as amodification to an existing DDS drive design as it requiressubstantially no modification of the circuitry of the group processor 52or DAT electronics 53. Instead, the embodiment relies on tapping intothe interconnection 80 (FIG. 3) which transfers G3 sub-groups betweenthe group processor 52 and DAT electronics 53.

As shown in FIG. 13, the interconnection 80 may be embodied as twouni-directional data lines 80A and 80B, the line 80A transferring G3sub-groups from the group processor 52 to the DAT electronics duringwriting and the line 80B effecting the reverse transfer during reading.These transfers are effected as continuous word streams as illustratedby FIG. 14D which shows G3 sub-group words on the interconnection 80,during valid periods as determined by a word clock signal WCK (FIG. 14B)generated by the DAT electronics 53. The word stream portion illustratedin FIG. 14D spans two G3 sub-groups, the start of each sub-grouptransfer over the interconnection 80 being determined by the frametiming signal FTS (FIG. 14A).

The first two words of each new G3 sub-group are the header words ofthat sub-group. As will be described below, a header timing signal HTS(FIG. 14C) can be generated from the FTS signal and word clock WCK toindicate the presence of the header words on the interconnection 80.

The time lines of FIG. 14E, F and G show the sixteen-bit data content ofthe two bytes of each word (FIG. 14G) in relation to a bit clock signalBCK (FIG. 14E) and the word clock WCK (FIG. 14F). The bit clock signalBCK is generated by the DAT electronics 53.

During data writing, the FIG. 13 embodiment examines the LF-ID in theheader of each G3 sub-group placed on line 80A by the group processor52. All non-amble sub-groups are allowed to pass from the groupprocessor 52 to the DAT electronics 53. For an amble sub-group the twoheader words are also allowed to pass unaltered; however, audio data isinjected in place of the remaining words of the amble sub-group. Duringdata reading, the FIG. 13 embodiment examines the LF-ID in each G3sub-group placed on line 80B and taps off the non-header portion ofamble sub-groups for audio processing.

Of course, during data reading, amble sub-groups occur on line 80B aswritten to tape initially and the FIG. 13 circuitry simply has toextract any audio data that may be present. In contrast, in order towrite audio data, it is necessary to take suitable measure to ensurethat the group processor 52 outputs sufficient amble sub-groups on line80A, it generally being inadequate to rely on normal operation of theDDS drive to produce the desired amble sub-groups. In fact, in standardDDS drives with SCSI interfaces (Small Computer System Interface) suchas that available from Hewlett-Packard Limited, it is possible tocommand the drive over the interface 50 to write successive groups of,for example, 25 ambles. This is possible using what is known as the`short erase` command (the reason for this name is that the writing ofambles effectively erases any data previously present on the tape). Theshort erase command is passed via the interface 50 to the systemcontroller 55 which, in turn, instructs the amble-control unit 45 of thegroup processor 52 to write 25 amble sub-groups. Short erase commandsmay be strung together to write any multiple of twenty five amble framesand provided the commands have their `immediate bit` set and eachcommand arrives within 15 ms of the previous one, the drive will`stream`, that is, write ambles without a break. Although a hostcomputer could be used to command amble generation in this manner, it ismore convenient to provide a local short-erase command input into thesystem controller 55 to permit local control of amble generation; such alocal command input is effectively a local "audio write" commandinasmuch as the resultant ambles can then be used for audio writing. Itwill, of course, be apparent to persons skilled in the art that theoutput of amble sub-groups can be commanded via the system controller 55without specifically using the short-erase command; for example, theamble-control unit 45 could be controlled to produce a continuous streamof ambles while audio data continues to be supplied to the drive.

Having described the general principle of operation of the FIG. 13embodiment, a detailed description will now be given of the audio-datainsertion/extraction circuitry.

The FIG. 13 circuitry comprises an amble body detector 81 arranged todetect and signal the presence of the non-header portion (the body) ofan amble G3 sub-group on the interconnection 80, an audio source 82, amultiplexor 83 for injecting the output of the audio source 81 into thewrite line 80A of the interconnection 80, and an audio sink 84 fortapping off and processing audio data from the read line 80B ofinterconnection 80.

The amble body detector 81 is fed with the signals on the operative oneof the lines 80A, 80B, this being line 80A during data writing and line80B during data reading. Line selection is effected by AND gates 85A,85B and OR gate 85C. The gate 85A is connected to line 80A, a enabled bya signal W asserted by the system controller 55 during data writing; thegate 85B is connected to line 80B and is enabled by a signal R assertedby the controller 55 during data reading.

The amble body detector 81 comprises an amble detector 86, a headerdetector 87, and output gates 88.

The amble detector 86 is fed with the signal on the operative line 80A/Bvia the gates 85. This signal is passed to a shift register 89, with anassociated decoder 90, for the purpose of capturing the header of eachG3 sub-group and determining whether its LF-ID is zero, therebyindicating an amble sub-group. The shift register 89 is clocked by theoutput of an AND gate 91 fed with the word and bit clock signals WCK andBCK. When the gate 91 is enabled by its third input, successive bits ofthe data words on the operative line 80A/B are clocked into the register89. The third, enabling input to the gate 91 is provided by the invertedoutput of a count-to-16 counter 92. This counter is arranged to be resetby the frame timing signal FTS following which its output is de-asserted(enabling gate 91) until a count of 16 is reached when its output isasserted (disabling gate 91). The counter 92 is clocked by the samesignal as the shift register 89. In operation, the counter 92 permitsthe first sixteen bits of each new sub-group (that is, the first headerword) to be clocked into the shift register 89 before disabling the gate91 and freezing the contents of register 89. The decoder 90 decodes theLF-ID bits of the first header word and if these bits corresponds to theamble frame ID of zero, the output of the amble detector is asserted. Agate 93 connected to the output of counter 92 prevents the ambledetector output being asserted until the first header word has beenfully clocked into the shift register 89.

The header detector 87 comprises a flip flop 94 arranged to be set bythe frame timing signal FTS and reset by the output of a count-to-twocounter 95 clocked by the falling edge of the word clock signal WCK. Thecounter 95 is reset by the signal FTS so that its output is asserted atthe end of the second word following the start of a frame, that is, atthe end of the G3 sub-group header. The non-inverted output of the flipflop 94 thus provides a header timing signal HTS of the form shown inFIG. 14C.

The output HTS of the header detector 87 and the output of the ambledetector 86 are combined in gate 88A to produce a signal that isasserted only during the non-header words of an amble sub-group (thatis, during the amble body). The gate 88A is an AND gate with aninverting input to which the signal HTS is connected. The amble bodysignal output by gate 88A is fed to two further AND gates 88B and 88Crespectively fed with the signals W and R. The output of gate 88Bconstitutes a write-amble-body (WAB) signal that is asserted when amblebody words are present on the write line 80A. The output of gate 88Cconstitutes a read-amble-body (RAB) signal that is asserted when amblebody words are present on the read line 80B.

The write-amble-body signal WAB is fed to an AND gate 96 together with asignal AUDW. This latter signal is asserted by the system controller 55whenever audio data is to be written to tape (the signal W will alwaysbe asserted when AUDW is asserted but not the other way around as it maynot be desired to write audio data during certain writing sessions).When both WAB and AUDW are asserted, the multiplexor 83 switches fromits normal state of transmitting words output by the group processor 52,to a state in which audio data words from the audio source 82 aretransmitted to the DAT electronics 53. In this manner, the non-headerwords of an amble sub-group are replaced by audio data words.

The audio source 82 comprises an analog input, an analog amplifier 97, alow-pass filter 98, and an analog-to-digital converter 99 clocked by theword and bit clocks WCK and BCK whereby to produce audio data wordssynchronized to the words on the line 80A.

Assuming the group processor 52 provides an uninterrupted succession ofamble sub-groups, audio data will be written to tape in much the sameway as DAT audio data with the exception that two words of everysub-group, namely the header words, are not audio data.

The read-amble-body signal RAB is fed to the audio sink 84 to enable thelatter during the non-header portions of amble sub-groups read from tapeand passed along line 80B. The audio sink 84 comprises adigital-to-analog (DAC) converter 100, a low-pass filter 101 and ananalog output amplifier 102. The DAC 100 is fed with the data words onthe operative line 80A/B and is clocked by the word and bit clocks WCK,BCK. However, the operation of DAC 100 is frozen unless the RAB signalis asserted. As a result, the DAC 100 is only operative to convert toanalog, amble body words read from tape. Any audio data present in ambleframes recorded to tape will thus be reproduced Note that when thesignal RAB is de-asserted during amble headers, the DAC 100 is arrangedto maintain its previous output, thereby to cover for the non-audioheader words.

In summary, to write audio data the DDS drive is caused to output ambleson write line 80A by a local `short erase` command (or in some othersuitable manner) The non-header portions of these ambles are detected bythe amble body detector 81 and signalled by signal WAB. As a result, themultiplexor 83 replaces the amble body words with audio data words.During reading, the amble body detector 81 detects the non-headerportions of ambles on read line 80B and indicates these portions bysignal RAB. This signal enables the audio sink 84 to convert to analogthe data words on line 80B.

A number of variations to the FIG. 13 embodiment are, of course,possible. For example, where the audio source 82 is not clocked by thedrive signals WCK, BCK but by an independent clock of the same nominalfrequency, then a first-in, first-out buffer will need to be provided tosmooth the flow of data between the source and multiplexor 83.Furthermore, the timing of the start of each G3 sub-group relative tothe FTS signal may differ from that shown in FIG. 14 (indeed, thistiming may differ between read and write operations). However, it iswell within the competence of persons skilled in the art to deviseappropriate clocking and writing circuitry to identify the start of eachsub-group and the header words within such a sub-group. Another possiblevariant would be to identify ambles by storing the LF-ID in a sub-code;indeed, according to the DDS format, byte 7 of pack item 3 contains theLF-ID and this pack item is stored in every frame; upon reading a tape,the drive could use this sub-code LF-ID to identify ambles rather thanmonitoring the headers for their LF-IDs.

The FIG. 13 embodiment has the advantage of requiring minimal changes toan existing DDS drive. However, where minimising design changes is notof overriding importance, another approach would be to insert/extractaudio data at the point of generation/removal of amble body dataitself--that is, within the amble-control unit 45 of the group processor52. In this case, the amble-control unit 45 is selectively operable in afirst, normal, mode to generate amble body data as a string of zeroes(standard amble), or in a second, audio, mode to generate amble bodydata by using audio data (audio amble). For audio ambles, the amble bodydata is extended to provide all words 1 to 1455 of a G3 sub-group and nopadding bytes are added in multiplexor 59 as is the case with standardambles. The amble headers are generated by the grouping unit 56 and arethe same for standard and audio ambles. The actual details of such animplementation will depend on the basic group processor design but,again, are well within the competence of persons skilled in the art. Oneadvantage of this particular implementation is that the audio data willbe randomized in randomizer 58 which is not the case for the FIG. 13embodiment.

As already indicated, the command of the drive to write ambles for thestorage of audio data can be done remotely from a host using theshort-erase command, or locally by providing for local input of thiscommand, or another command causing amble generation, to the systemcontroller 55 This local input case is preferred as it enables the driveto be used independently of any host to read/write audio data. For localcontrol purposes, the drive can be provided with a local interface tothe system controller enabling all required functions to be implemented,such as "audio write" (generation of a command to the amble-control unit45 causing ambles to be produced; generation of signals W and AUDW forFIG. 13 embodiment), "audio play" (generation of signal R for FIG. 13embodiment), "rewind" and "eject".

The foregoing description has concentrated on the storage of audio datain ambles. However, instead of audio data, other auxiliary data,including asynchronous data, can be stored in the ambles. Where the datais asynchronous, it would be possible to arrange for a fixed number ofamble frames to be generated following each group and to use theseframes for storing the auxiliary data (it is unlikely that such anarrangement would be suitable for synchronous data particularly where aread-after-write recording method is used in which bad frames within agroup are rewritten causing the groups to have an indeterminate numberof physical frames). For small amounts of asynchronous data, it may incertain circumstances be possible simply to rely on ambles generatedduring the normal course of operation of a DDS drive.

It is also possible to arrange for the auxiliary data which is to bewritten into the ambles, to be derived from any one of a number ofdifferent sources. In this case, input selection means 105 shown indashed lines in FIG. 13 may be provided having a selection control input107; audio data would then be just one possible selectable source. Inorder to facilitate source identification, the input selection means canbe arranged to include into the selected auxiliary data, a sourceidentifier, for example, at a predetermined word position (the requisitetiming signals for effecting the insertion of such a source identifierare not shown in FIG. 13 but their generation and utilization will beapparent to persons skilled in the art).

Where multi-source auxiliary data is written to tape, output selectionmeans 106 (shown dashed in FIG. 13) are preferably provided in the linetapped off the read-line 80A. The output selection means is arranged torecognise the source identifier included in the auxiliary data and todirect the output of this data appropriately.

As an alternative to including a source identifier in the auxiliary dataitself, this information could be written in a preceding group as `host`data either via the host or by modification of the FIG. 3 drive topermit local writing of data into groups.

Indeed, any data about the auxiliary data stored in ambles, can bewritten in a normal group that precedes (or follows) the ambles. Thus,where the auxiliary data is audio data, a plurality of audio passages(`tracks` in normal audio record parlance) can be stored on tape eachpreceded by a group containing a filemark identifying the audio track.An index to tracks could then be stored in the first group enabling auser to select a track which the drive is then arranged to access via afast search on filemarks, and play.

The interleaving between host data and audio lends itself toeducational/documental applications. For instance, if the group datapreceding an audio amble area is a computer program (which would be runby the host upon loading) containing a diagram, picture or animation,then the following audio could be a commentary on or explanation of thedisplayed material.

Finally, it will of course be appreciated that although the foregoingdescription has been given in terms of a drive generally implementingthe DDS format, many of the details of that format are not relevant tothe present invention or its preferred embodiment described above. Thusfor example, at a low level the exact nature of the polynomialcharacterizing the randomizer is not relevant to the present inventionand above described preferred embodiment of the invention is independentof this polynomial. More generally, however, the present invention isapplicable to drives implementing other formats where tracksimplementing auxiliary functions, such as group separation and/orpadding, are capable of being used to store auxiliary data.

We claim:
 1. A tape storage device comprising:helical-scan recordingmeans operative to write to tape in a succession of tracks each having adata area for the storage of data, and signal processing means operativeto receive first data signals, representative of first data to bestored, and to process said first data signals to generate and outputtrack signals to said recording means whereby to cause the latter towrite the first data to tape in accordance with a predetermined formatin which said first data is stored in the data areas of one or moregroups of tracks with further tracks, hereinafter "amble" tracks, beingused to perform auxiliary functions including bufferizing/paddingfunctions, the said groups of tracks and said amble tracks includingidentifiers distinguishing them from each other; said signal processingmeans including insertion means arranged to receive second data signals,representative of second data to be stored, and operative to cause saidsecond data to be written in the data areas of amble tracks; whereinsaid first and second data signals are received from externally of saidtape storage device; and said signal processing means comprises a firstwrite-processing section arranged to receive said first data signals andto generate intermediate signals for constituting the data areas both ofsaid groups of tracks and of said amble tracks, and a secondwrite-processing section operative to produce said track signals fromsaid intermediate signals; said insertion means including: ambledetection means connected to monitor said intermediate signals wherebyto detect the signals for constituting said amble data areas; andmultiplexor means connected to receive both said intermediate signalsand said second data signals and selectively operable to pass one orother of these signals to said second write-processing means; the ambledetector means being connected to control said mulitplexor means suchthat said intermediate signals are normally passed to said secondwrite-processing means with said second data signals only being passedto the second write-processing means during the time, or a portionthereof, when the amble-data-area signals are detected.
 2. A tapestorage device according to claim 1, wherein said insertion means isoperative when second data is to be stored, to cause said signalprocessing means to generate a succession of amble tracks storing thesecond data.
 3. A tape storage device according to claim 1, wherein saidfirst write-processing section is operative to generate, as part of saidintermediate signals, identification signals for distinguishing betweensaid groups of tracks and said amble tracks, said insertion means beingoperative to allow said identification signals, including thoseassociated with amble tracks, to pass unaltered to said secondwrite-processing means.
 4. A tape storage device according to claim 1,wherein said recording means is operative to write tracks in pairshereinafter referred to as "frames", said signal processing meansincluding header means for generating for each frame a header includingan identifier indicative of whether the frame contains tracks storingfirst data or amble tracks, the signal processing means being operativeto store the headers generated by the header means in the correspondingframes.
 5. A tape storage device according to claim 1, wherein saidsecond data is audio data, the storage device including audio inputmeans for providing a digitized audio signal as said second data signal,the audio digitization being synchronized with the operation of saidrecording means.
 6. A tape storage device according to claim 1, whereinsaid second data is derived from any one or more of a plurality ofsources, the storage device including input selection means forselecting between a plurality of different input sources for theprovision of said second data, and means for storing a source identifiereither as part of said second data or as first data in an associatedsaid group of tracks.
 7. A tape storage device for reading first datathat has been written to tape in accordance with a predeterminedrecording format in which the tape is written using a helical-scanrecording method to form a succession of tracks each of which has a dataarea for the storage of data, said first data being stored in the dataareas of one or more groups of tracks with further tracks, hereinafter"amble" tracks, being used to perform auxiliary functions includingbuffering/padding functions, the said groups of tracks and said ambletracks including identifiers distinguishing them from each other saidstorage device comprising:helical-scan reading means operative to readsaid tape and to output track signals representative of the tracksrecorded thereon, and signal processing means operative to receive saidtrack signals from the helical-scan reading means and to process saidtrack signals to generate and output first data signals representativeof said first data recorded in the data areas of said groups of tracks,said processing involving distinguishing signals derived from saidgroups of tracks from signals derived from said amble tracks whereby toavoid any contents of said amble tracks being treated as first data;said signal processing means including extraction means operative toextract from the data areas of said amble tracks any second data writtentherein and to generate and output second data signals representative ofany such second data; wherein said signal processing means comprises afirst read-processing section arranged to receive said track signals andto generate intermediate signals representative of the contents of thedata areas both of said groups of tracks and of said amble tracks, and asecond read-processing section operative to produce said first datasignals from said intermediate signals; said extraction means including:amble detection means connected to monitor said intermediate signalswhereby to detect the signals representative of the contents of saidamble data areas, and output means connected to receive saidintermediate signals and controlled by said amble detection means toutilize said signals representative of the contents of said amble dataareas as the second data signals.
 8. A tape storage device according toclaim 1, wherein said tracks have been written to tape in pairshereinafter referred to as "frames", each frame having an associatedheader including an identifier indicative of whether the frame containstracks storing first data or amble tracks, the signal processing meansbeing operative to monitor the headers to differentiate data written insaid groups of tracks from data written in said amble tracks.
 9. A tapestorage device according to claim 1, wherein said second data is audiodata, the storage device including audio data output means.
 10. A tapestorage device according to claim 1, wherein said second data is derivedfrom any one or more of a plurality of sources and a source identifieris stored as part of said second data or as first data in an associatedsaid group of tracks, the storage device including output selectionmeans responsive to said source identifier to select between a pluralityof different outputs for said second data.
 11. A tape storage deviceaccording to claim 1, wherein said predetermined format is substantiallyin accordance with the Digital Data Storage Format including header andnon-header portions but the tape storage device including means forreplacing the non-header portions of the data areas of at least someamble tracks with said second data.
 12. A tape storage device,comprising:(a) helical-scan means for writing data to tape in asuccession of tracks each having a data area for the storage of data;(b) signal processing means for receiving first data signalsrepresenting first data to be stored and for processing said first datasignals to generate and output track signals to said helical-scan meansto cause said helical-scan means to write the first data to tape inaccordance with a predetermined format in which said first data isstored in the data areas of one or more groups of tracks with ambletracks for performing auxiliary functions including bufferizing/paddingfunctions, the said groups of tracks and amble tracks beingdistinguishable from each other by identifiers contained therein; (c)audio input means for providing a digitized audio data signalrepresenting audio data; and (d) insertion means for receiving saidaudio data signal and for causing said audio data to be written in thedata areas of amble tracks; wherein:(1) said signal processing meansincludes:a group processor section arranged to receive said first datasignals and to generate intermediate signals for constituting the dataareas both of said groups of tracks and of said amble tracks, and adigital audio tape (DAT) electronics section operative to produce saidtrack signals from said intermediate signals; (2) said insertion meansincludes:amble detector means for monitoring said intermediate signalsand detecting said amble data areas, and mulitplexor means for receivingboth said intermediate signals and said audio data signals andselectively passing these signals to said DAT electronics section, theamble detector means being coupled to control said mulitplexor meanssuch that said intermediate signals are normally passed to said DATelectronics means and said audio data signals are only passed to the DATelectronics means during the time, or a portion thereof, when the ambledata areas are detected; and (3) said group processor means is operativeto generate, as part of said intermediate signals, identificationsignals for distinguishing between said groups of tracks and said ambletracks, said insertion means being operative to allow saididentification signals, including those associated with amble tracks, topass unaltered to said DAT electronic means.
 13. A tape storage deviceaccording to claim 12, further comprising insertion means for causingsaid signal processing means to generate a succession of amble tracks.14. A tape storage device according to claim 12 wherein saidhelical-scan means is operative to write tracks in frames and furthercomprising:means for generating for each frame a header including anidentifier indicative of whether the frame contains tracks storing firstdata or amble tracks; means for storing the headers in the correspondingframes; input selection means for selecting between a plurality ofdifferent input sources for the provision of said audio data; and meansfor storing a source identifier either as part of said audio data or asfirst data in an associated group of tracks.
 15. A tape storage devicecomprising:helical-scan formatting the recording means operative toformat signals fed thereto and to write these formatted signals to tapein a succession of tracks each having a data area for the storage ofdata, and signal processing means comprising: first processing meansoperative to receive from externally of said device first external datasignals, representative of first data to be stored, and to process saidfirst external data signals to generate and output first intermediatedata signals to said formatting and recording means whereby to cause thelatter to write the first data to tape in the data areas of one or moregroups of tracks, each said group of tracks including a first identifierfor identifying these tracks as such; amble means for generating andoutputting amble signals to said formatting and recording means wherebyto cause the latter to write tracks, hereinafter "amble tracks", withinternally-provided dummy data in their data areas and each including asecond identifier different from said first identifier whereby to enablethe said groups of tracks and said amble tracks to be distinguished fromeach other upon reading; second processing means operative to receivefrom externally of said device second external data signals,representative of said data to be stored, and to process said secondexternal data signals to generate and output second intermediate datasignals to said formatting and recording means whereby to cause thelatter to write the second data to tape in the data areas of one or morefurther tracks, each said further track including a said secondidentifier enabling these tracks to be distinguished from said groups oftracks upon reading; and control means for coordinating operation ofsaid first processing means, said amble means, and said secondprocessing means.
 16. A tape storage device according to claim 15,wherein said second processing means includes:detector means formonitoring said amble signals output by said amble means whereby togenerate an enable signal indicative of the presence of portions of saidamble signals corresponding to the data areas of intended said ambletracks, and multiplexer means connected to receive both said amblesignals and said second intermediate data signals and selectivelyoperable to pass a selected one of these signals to the formatting andrecording means, the detector means being connected to control saidmultiplexor means such that said amble signals are normally passed tosaid formatting and recording means with said second intermediate datasignals only being passed to the formatting and recording means duringthe time, or a part thereof, when said enable signal indicates thepresence of said portions of the amble signals corresponding to ambletrack data areas.
 17. A tape storage device according to claim 16,wherein said amble means generates as part of said amble signalssecond-identifier signals for producing said second identifiers, saidsecond-identifier signals being outside of the said portions of saidamble signals corresponding to the data areas of the intended ambletracks whereby said second-identifier signals pass through saidmultiplexer means to said formatting and recording means.
 18. A tapestorage device according to claim 16, wherein said control means isoperative to cause said amble means to output sufficient amble signalsto accommodate said second intermediate data signals.
 19. A tape storagedevice according to claim 15, wherein said second data is audio data,the storage device including audio input means for providing a digitizedaudio signal as said second data signal, the audio digitization beingsynchronized with the operation of the recording means.
 20. A tapestorage device according to claim 15, wherein said second data isderived from any one or more of a plurality of sources, the storagedevice including input selection means for selecting between a pluralityof different input sources for the provision of said second data, andmeans for storing a source identifier either as part of said second dataor as first data in an associated said group of tracks.